Tom Jr. - Posted - 07/07/2009:  06:21:37

I have fought with bending sides on some difficult and stiff woods and was wondering how everyone else is doing their side bending. I only make something every couple years and haven't coughed up the money for a heating blanket. I have used a pipe with a torch blowing in it, steam bending, and slowly clamping down over a hot form after soaking in a four foot stretch of gutter sitting on the stove.
After bending some black locust over a form after being soaked and steamed, it rebounded nearly straight. I had to free form that over a pipe with dripping water and bending nearly 180 degrees to get the any kind of shape to stay. The results are not perfectly symmetrical at my current level of inexpertise.
Is there a consensus on how "bent" the sides should be. Should they just lay right on top of the back with no tension (perfectly shaped) or should they need to be squeezed in a bit and be under some tension?

Don''t squat with your spurs on.

davidmaulik - Posted - 07/07/2009:  08:43:11

I am no expert at side bending either in fact I haven't had much luck and the most challenging material that I have bent is maple (so far anyway). From I think the best sounding instrument would have sides that do not have any tension in them, however I feel that a small amount of tension should not effect the sound too much. The biggest concern that I have with tension in the sides is the amount of strain that is placed on the glue joint where the top and back meet the sides. For this reason I always overbend the sides so when the wood springs back it is approximately where I want them to end up.

Tom Jr. - Posted - 07/07/2009:  10:00:57

A standard acoustic guitar top and back are both under tension typically which is necessary for good sound production. Sides are not know for being big sound producers but I would like to squeeze out every little bit I can. I put a back in a reso under tension, i.e. a flat board with radiused bracing.
One train of thought is that under tension, there is minimal slack to absorb and dampen any sound waves.
If you are overbending to get the sides where you want them, I suppose you are bending around a heated pipe of some sort. What size are you using?

Don''t squat with your spurs on.

davidmaulik - Posted - 07/09/2009:  07:39:55

I am bending over a 3 1/2" pipe that has been "carefully" pounded into an "egg" shape.

The reason that I do not try to put tension in the sides is that the sound waves on a top are moving the top up and down (perpendicular to the strings), the same for the back, but I have always felt that the sides move in and out (parallel to the strings). I believe the sides transmit the sound to the back from the top. I think that a top under tension acts against the string downward string pressure. I also feel that the sides are acting against the pressure of the strings but if you were to put them under tension they would be acting against the top and back glue joints. But like I said before I am no expert and this is just a mix of what I have read and what seems to make sense.